Team Sky’s duds during the Stage 1 time trial caused an outcry. Detractors claim that dimples on the arms and shoulders of the skinsuits worn by Chris Froome, Geraint Thomas (who eventually won the stage), Michael Landa, and Vasil Kiryienka flout Article 1.3.033 of the UCI rules which states, “it is forbidden to wear non-essential items of clothing or items designed to influence the performances of a rider such as reducing air resistance or modifying the body of the rider.”

On Monday, French sports paper L’Equipe ran a front-page story on the skinsuit with the headline “Excessive Speed.” Other teams, including French outfit Française des Jeux (FDJ), pointed to a number of dimple-covered panels on the skinsuit and argued that they broke the UCI’s rule. The UCI looked into the matter following the time trial and ruled that the suit was legal.

That hasn’t stopped claims to the contrary. The Castelli-made skinsuit certainly does dance on the line between legal and illegal, but Steve Smith, Castelli’s brand manager, says the controversy is much ado about nothing.

“The dimples seem to have a far greater psychological impact than an aero effect,” he says of the dotted fabric on the shoulders and arms of the suit. In fact, Smith says there’s much more to the skin suit than just the dimpled fabric, but it’s those dots that critics have latched onto as an indication that Sky riders are getting an unfair advantage. That’s because the UCI rule states nothing can be added to a piece of clothing to aid in aerodynamics. Smith says nothing has been added, so the argument is moot.

What about those dimples?

First, let’s talk about how it works. Air slows down as it flows over a rider’s body, causing friction. That slows the rider down. In order to move that air more swiftly, the dimples create tiny vortices to keep the fast-moving air closer to the rider’s body for a longer period of time, before it separates and causes drag. This concept is called flow separation, and it’s nothing new in aerodynamic design.

The UCI rule clearly states that non-essential items that improve aerodynamics cannot be added to clothing. But Smith says despite the appearance, the dimples are actually part of the fabric itself, not an addition. “The dimples are in the fabric, not on them,” he says. “The way the rules are written, we didn’t even think it would apply to what we were doing. The dimples do not fundamentally change the shape of the cyclist.” Smith wouldn’t reveal the process by which the dimples are formed.

Breaking it down

That UCI rule contains three essential components:

1 — Non-essential items of clothing
2 — Items designed to influence the performances of a rider such as reducing air resistance
3 — Modifying the body of the rider

If the dimples are part of the skinsuit itself, and a skinsuit is an essential item, then the skinsuit appears to be legal according to part 1.

If the dimples do not modify the body shape of the rider — if a rider shoved a fairing over his back, that would certainly be a problem — then the skinsuit appears to be legal according to part 3.

But it’s that second part that seems ambiguous. The dimples do, by Castelli’s admission, reduce air resistance at certain speeds. The real question is whether the dimples count as an “item.”

Smith says no, arguing the dimples are part of the skinsuit’s structure, not an item independent of that fabric.

There’s one more reason Castelli and Team Sky might be able to logically get around Part 2: Smith is quick to note that the skinsuit might actually slow down all but the fastest riders in the world. In testing, the skinsuit did not offer gains below a certain wind speed, so Smith says only the fastest pros truly gain anything from the suit. Does that mean the dimples don’t reduce air resistance for certain riders? That’s entirely possible. After his stage win, Geraint Thomas told Cycling Weekly, “At the end of the day, you can borrow the skinsuit if you want and see what time you do.”

When VeloNews asked how much savings there would be over 40 kilometers, Smith wouldn’t give an exact number but said the gains would be “significant” for the fastest riders on the planet — like those who took part in the opening time trial of the Tour de France.

In the end, the controversy appears to be more of an indictment of the UCI rule’s ambiguity than the skinsuit itself.

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